/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.streaming.api.functions.co;
import java.io.Serializable;
import org.apache.flink.annotation.Public;
import org.apache.flink.api.common.functions.Function;
import org.apache.flink.util.Collector;
/**
* A CoFlatMapFunction implements a flat-map transformation over two
* connected streams.
*
* <p>The same instance of the transformation function is used to transform
* both of the connected streams. That way, the stream transformations can
* share state.
*
* <p>An example for the use of connected streams would be to apply rules that change over time
* onto elements of a stream. One of the connected streams has the rules, the other stream the
* elements to apply the rules to. The operation on the connected stream maintains the
* current set of rules in the state. It may receive either a rule update (from the first stream)
* and update the state, or a data element (from the second stream) and apply the rules in the
* state to the element. The result of applying the rules would be emitted.
*
* @param <IN1> Type of the first input.
* @param <IN2> Type of the second input.
* @param <OUT> Output type.
*/
@Public
public interface CoFlatMapFunction<IN1, IN2, OUT> extends Function, Serializable {
/**
* This method is called for each element in the first of the connected streams.
*
* @param value The stream element
* @param out The collector to emit resulting elements to
* @throws Exception The function may throw exceptions which cause the streaming program
* to fail and go into recovery.
*/
void flatMap1(IN1 value, Collector<OUT> out) throws Exception;
/**
* This method is called for each element in the second of the connected streams.
*
* @param value The stream element
* @param out The collector to emit resulting elements to
* @throws Exception The function may throw exceptions which cause the streaming program
* to fail and go into recovery.
*/
void flatMap2(IN2 value, Collector<OUT> out) throws Exception;
}